Modeling means that a model is created from an article/structure under design for describing the article/structure to be constructed, the model containing at least information needed to illustrate the article/structure. The development of data processing systems and computers has transformed modeling into a computerized process, where a product model is created from the article/structure. A wide variety of software applications, including computer-aided design applications and three-dimensional modeling applications, are currently available to end-users to prepare or edit a model, and/or to obtain necessary information from the model. For example, in building industry, a model of a building may be edited and/or used in several phases for different purposes by different persons: on a planning phase to combine plans from different designers (architects, structural engineers, designers for planning of heating plumbing ventilation and sanitation), who can see what the others have planned, and take that into account in their own design work; on a construction phase, a construction worker on a construction site will have exact plans and drawings, created from the information in the model, to facilitate and ensure that building elements/structural components will be placed on proper places and have proper size; on a maintenance phase the right information about the building, for example were plumbing pipes are and what is their size, is available to the maintenance team from the information in the model.
A building, and therefore also a model of building, comprise many building elements/structural components, such as columns, beams, slabs, walls, which in turn may comprise smaller structural components. For example, concrete structures, such as floor slabs and walls, incorporate into the model a very large number of physical reinforcement elements, such as steel bars (“rebars”). Typically each structural component is modeled as a fully modeled three-dimensional physical element. While this allows for accurate renderings in plan and section views and accurate amount information for manufacturing, it involves storing redundant information thereby increasing the memory size required by a 3D model, and need for processing power.